1. Field of the Invention
This invention relates to new and useful improvements in earth boring apparatus and more particularly to earth boring augers provided with an auxiliary means for penetrating rocks and other hard formations.
1. Description of the Prior Art
Power driven earth boring augers are commonly used for drilling holes in the earth in soft formations. Augers are used from small sizes of the order of 1 or 2 inches up to large sizes which may be several feet in diameter. Augers are used for drilling holes in soft formations in depths up to about 150 feet. Auger drilled holes are used in foundations for buildings and for other construction purposes and are also used for various types of wells and blast holes.
In drilling through rock and other hard formations, it is ordinarily not possible to use augers. For hard formations, it is necessary to use hard rotary rock drills, roller bits, or rotary pneumatic hammers.
While augers have proven quite effective for drilling soft formations and various types of rock drills are quite effective in hard formations, there has been no generally satisfactory method for drilling through formations that are heterogenous in structure. Thus, if it is desired to drill through a formation which is alternately hard and soft or a soft formation which contains boulders or even smaller rocks or occasional layers of hard material there is no generally satisfactory drilling method available. An auger can be used in the softer formations and then a rock type drill used for drilling through rock or harder formations. This is quite costly and inefficient in operation. There has been a considerable need for a single type of drilling apparatus which will be effective both in soft and harder formations without necessitating frequent changes in the type of drill used.